You have the choice of initializing and activating a new swap partition, activating a previously-initialized one, or doing without a swap partition.
"Debian GNU/Linux: Guide to Installation and Usage"
John Goerzen and Ossama Othman
About the only reason to mount a partition without initializing it at this point would be to mount a partition upon which you have already performed some part of the installation process using this same set of installation floppies.
"Debian GNU/Linux: Guide to Installation and Usage"
John Goerzen and Ossama Othman